Do you think the Pharisees are trying to protect Jesus here? Me either. My guess is they are trying to set their own trap for him. Jesus tells them he will leave when he is ready. After all, his whole life is being orchestrated by God himself. Jesus is heading toward Jerusalem, but in his own time.
Jerusalem was the spiritual and political capital of the region, a city of God, the hub of the nation. It was a destination for many believers. It was also the death sentence location for many prophets over the years. There’s a bit of foreshadowing going on when Jesus declared, “For it wouldn’t do for a prophet of God to be killed except in Jerusalem!” Here, he is calling himself a prophet, or putting himself in that category, because of who people believed him to be.